The use of rotatably driven grinding wheels is widespread and familiar in our industrial society. One of the more serious problems encountered in the use of such devices resides in the provision of effective means for preventing undesired of accidental disassociation of the griding wheel from the shaft, spindle or other rotatable drive means on which it is mounted. This problem is particularly acute when the connection between the grinding wheel and its driving shaft or spindle is intentionally detachable to facilitate quick removal and replacement of the grinding wheel. Into this category fall a host of devices, for example, portable powered grinders wherein the grinding wheels employed are intentionally detachable from the power driven shaft so that they may be readily replaced. To properly mount the grinding wheel upon the shaft provision must be made to provide sufficient clamping force and also to secure the wheel rotationally.
One means of securing the grinding wheel to the drive shaft has been to provide an appropriate backing flange with a central opening which is aligned with an opening provided in the depressed center abrasive grinding wheel. A bolt or nut member (depending upon the configuration of the drive shaft, that is, whether it is externally or internally threaded) is inserted from the face side of the grinding wheel and is then tightened in place. In this manner a plurality of loose parts are configured in a completed assembly ready for use. As the grinding wheel is utilized the appropriate clamping force is provided to securely affix the grinding wheel to the drive shaft. Such an assembly, however, typically requires appropriate tools such as wrenches or the like to remove the grinding wheel from the drive shaft.
Subsequently it became desirable to affix the mounting hub permanently to the grinding wheel so that the entire unit may be quickly and easily attached and detached from the drive shaft and discarded when the grinding wheel has been worn down. In these types of devices it is customary to utilize an adhesive such as an epoxy resin or the like between the backing flange and the back surface of the grinding wheel to retain integrity between the mounting hub and the grinding wheel to secure the wheel rotationally.
Even though the adhesive tended to work quite well in most applications, it was discovered that in some instances the adhesive would break loose and the grinding wheel would rotate relative to the mounting hub. Such was particularly the case since the hub was a one-piece member which was internally threaded and held in place upon the grinding wheel by swaging an extension thereof into place, thus providing a fixed clamping force holding the grinding wheel. No additional clamping force was exerted during further rotation of the wheel during use as was the case with the traditional nut which was secured from the face as above described. As a result various keyways and corresponding key structures were developed between the wheel and the mounting hub and used in conjunction with the adhesive to preclude rotational movement between the mounting hub and the grinding wheel.
Prior art patents disclosing the foregoing structures are U.S. Pat. Nos. 3,041,797; 3,081,584; 3,136,100; 3,210,892; 3,596,415; 3,879,178; 4,015,371 and 4,541,205.
The devices utilized in the prior art for providing the disposable grinding wheel assembly including the permanently affixed mounting hub generally provide the service intended. There are certain inherent disadvantages found with regard to the various devices. Such disadvantages are that in manufacturing the utilization of an epoxy adhesive adds additional labor to the cost of manufacturing. In certain of the devices, parts must be keyed together and properly aligned in order to function appropriately. In addition thereto, through the utilization of die-cast mounting hubs which include as an integral part the backing flange there is no additional clamping force exerted upon the grinding wheel as it is being rotated by the power tool. Furthermore, such die-cast mounting hubs are relatively bulkly, take up space and add substantial weight and additional cost to the completed product.